Many vehicles now utilize hybrid-electric powertrains in order to increase the efficiency of the vehicle. Hybrid-electric powertrains typically improve overall vehicle fuel efficiency by allowing supplementing an internal combustion engine with electric motors, such that less power output is required of the internal combustion engine, as power from the electric motors may also be utilized in situations when maximum powertrain output is required, such as acceleration, or climbing a grade. Additionally, hybrid-electric powertrains may be utilized to power equipment mounted to a vehicle, such as, for example, a lift, an auger, a post hole digger, a crane, or other known equipment that may be utilized when a vehicle is not in motion. Such power equipment may be powered through a power take off (“PTO”) that may be driven by electric motors of the hybrid-electric powertrain to reduce the time an internal combustion engine is operated.
The initiation and de-initiation, or startup and shutdown, of the electrical systems in a vehicle having a hybrid-electric powertrain presents issues not experienced previously. For instance, during initiation of electrical systems, simply transitioning high-voltage isolation contactors from an open state, which prevents the flow of electricity, to a closed state, which allows the flow of electricity, upon activation of a vehicle's key, may cause a rapid uncontrolled free flow of electrical energy that may damage system components. For example, design limits of system components may be exceeded by rapid loading of electrical energy, thereby damaging the system components. Similarly, when electrical systems are de-initiated, premature component failure or excessive battery discharge may occur if the flow of electrical energy is suddenly stopped.
Further, in addition to initiation and de-initiation of the electrical systems, voltage of individual cells in batteries of the hybrid-electric powertrain needs to be balanced to allow the electrical system to function as intended and to allow the battery packs to offer performance and life cycle that is acceptable. If voltage of the individual battery cells is not kept within a certain range, battery pack life may be adversely affected, and electrical systems may not have sufficient voltage if one of the individual cells in a battery pack is not as charged as the rest of the cells. Previous efforts to provide battery management systems focused on either balancing voltage within the battery cells after the vehicle had been shut off, which can drain the battery packs to a level to prevent the vehicle from starting, or the battery management system is active during operation of the hybrid-electric powertrain, which makes it increasingly difficult to balance the battery packs as electric loads are constantly varying the voltage within the battery packs.
Therefore, a need exists for a control system that controls the initiation, de-initiation, and battery management system for an electrical system of a vehicle having a hybrid-electric powertrain.